This application is based upon and claims priority of Japanese Patent Application No. 2001-31339, filed on Feb. 7, 2001, the contents being incorporated herein by reference, and a continuation of PCT/JP02/01048, filed Feb. 7. 2002.
The present invention relates to an axial fan, for vehicles, having a plurality of blades radially extending from a boss (hub).
A radiator, and a blower for blowing cold air onto the radiator, have usually been mounted on the portions where the air can be easily taken in, such as at the front end of the vehicle. Therefore, the blower is strongly affected by the air pressure caused by travelling of the vehicle.
Concretely speaking, the axial fan used for the blower is such that the air passes through in the axial direction. When the air pressure caused by travelling of the vehicle is received in the axial direction, therefore, the velocity differential becomes small between the surfaces of the blades and the air, and the resistance becomes small between the blade surfaces and the air.
In an idling condition in which the vehicle is at rest while the axial fan (blower) is in operation, on the other hand, the resistance is great between the blade surfaces and the air when there is almost no air pressure caused by travelling of the vehicle. On the root side of the blades 212 where the peripheral velocity is small, therefore, the air flow peels off the surfaces of the blades 212 and stalls. As shown in FIG. 7, therefore, the air that is blown fails to flow in the axial direction but flows in an outer radial direction.
As the air that is blown flows in the outer radial direction, the spatial size W1 through which the air substantially flows becomes smaller than the spatial size Wo in which the air substantially flows when the air that is blown is flowing in the axial direction, resulting in a decrease in the blow rate and in the fan efficiency of the blower.
This phenomenon (problem) occurs particularly conspicuously when there exists a wall surface having a large air resistance, such as an engine, on the downstream side of the axial fan.
In view of the above-mentioned points, therefore, it is an object of the present invention to provide an axial fan for vehicles, which suppresses a drop in the flow rate that occurs when the air that is blown does not flow in the axial direction but flows in the outer radial direction.
In order to accomplish the above-mentioned object according to one aspect of the present invention, there is provided an axial fan 210, having a plurality of blades 212 radially extending from a boss 211 to blow the air to a heat exchanger 100 mounted on the vehicle, wherein the axial end surface 211a of the boss 211 on the negative pressure side 212 of the blades 212 is so constituted that the air flows toward the root side of the blades 212 from the side of the axial end surface 211a. 
Due to the air flowing toward the root side of the blades 212 from the side of the axial end surface 211a, therefore, the resistance decreases between the air and the blade surfaces on the root side of the blades 212, making it possible to prevent a stall on the root side of the blades 212. It is, therefore, possible to effectively make the air on the front side of the boss 211 flow toward the outer direction (toward the blades 212) and, hence, to suppress a drop in the flow rate.
According to another aspect of the present invention, there is provided an axial fan 210, having a plurality of blades 212 radially extending from a boss 211 to blow the air to a heat exchanger 100 mounted on the vehicle, wherein the front edges 212b of the blades 212 are deviated toward the upstream side in the air stream beyond the axial end surface 211a at the axial end of the boss 211 as viewed from a direction at right angles to the axial direction of the boss 211.
It is thus made possible for the air to flow from the side of the axial end surface 211a toward the root side of the blades 212. Due to the air flowing toward the root side of the blades 212 from the side of the axial end surface 211a, therefore, the resistance decreases between the air and the blade surfaces on the root side of the blades 212. It is, therefore, allowed to effectively guide the air on the front side of the boss 211 toward the outer direction (toward the blades 212) and, hence, to suppress a drop in the flow rate.
The invention can be more fully understood from the accompanying drawings and from the description of preferred embodiments of the invention.